GA Flood Risk & Social Vulnerability
An Exploration of County & Census Tract Impacts
Shikha Srinivas, Community Resilience Data Intern, Re:Public; Justin Cross, Data Science Intern, Re:Public; Max Evans, Head of Product and Geospatial Data, Re:Public
This virtual link is meant to supplement Re:Public’s poster at the 2021 Georgia Climate Conference. It contains interactive graphics which included screencaps on the poster as well as a few additional charts.
The datasets used include the National Flood Hazard Layer for a 100-year flood by extent, the CDC’s Social Vulnerability Index (1), and Re:Public’s database of flooded community lifelines (accessed December 2020).
Flood Claims in GA
The map below shows the number of flood claims by tract.
The table below shows the counties with the most flood claims in the last ~50 years.
| County | Number of Redacted Claims | Number of Building Claims |
|---|---|---|
| Chatham | 5173 | 3664 |
| Fulton | 2830 | 2153 |
| DeKalb | 1942 | 1367 |
| Glynn | 1894 | 1277 |
| Cobb | 1819 | 1320 |
| Dougherty | 1239 | 953 |
| Lee | 648 | 551 |
| Richmond | 498 | 388 |
| Gwinnett | 468 | 351 |
| Floyd | 374 | 273 |
County Flooding and SVI
The interactive map below shows the CDC’s SVI overall vulnerability percentile (ranked at the national level) by county.
The table shows the 10 most vulnerable counties in the state.
| County | Vulnerability Percentile |
|---|---|
| Mitchell County, Georgia | 0.9879 |
| Crisp County, Georgia | 0.9857 |
| Evans County, Georgia | 0.9847 |
| Candler County, Georgia | 0.9828 |
| Colquitt County, Georgia | 0.9812 |
| Turner County, Georgia | 0.9809 |
| Clinch County, Georgia | 0.9777 |
| Calhoun County, Georgia | 0.9774 |
| Emanuel County, Georgia | 0.9768 |
| Sumter County, Georgia | 0.9764 |
The following scatterplot shows how overall vulnerability (percentiles taken at the national level) compares to county area flooded. 
The interactive map below shows county and percent flooding by land area.
The list below outlines the 10 most flooded counties by land area in Georgia.
| County | Area Flooded (%) |
|---|---|
| Chatham | 59.70837 |
| Liberty | 58.02474 |
| McIntosh | 57.64067 |
| Bryan | 56.55048 |
| Glynn | 52.41560 |
| Ware | 52.30268 |
| Long | 51.33037 |
| Charlton | 49.60163 |
| Clinch | 49.17702 |
| Camden | 45.50368 |
The map below shows the percent of community lifelines (critical infrastructure) in the floodplain of a 100-year flood by county.
The list below the counties experiencing the largest amount of infrastructure flooding.
| County | Infrastructure Flooded (%) |
|---|---|
| Rabun | 46.00000 |
| Gilmer | 40.22989 |
| Fannin | 39.28571 |
| Stewart | 39.07285 |
| McIntosh | 38.75000 |
| Pulaski | 38.46154 |
| Oglethorpe | 37.81513 |
| Colquitt | 37.54789 |
| Worth | 36.89320 |
| Clinch | 35.05155 |
The following maps show impacted lifelines by type and county for the top 5 most well-defined community lifelines in FEMA’s dataset.
| County | Communication Infrastructure Flooded (%) |
|---|---|
| Bryan | 34.04255 |
| Seminole | 31.57895 |
| Miller | 30.00000 |
| Cook | 26.82927 |
| Chatham | 23.00885 |
| County | Energy Infrastructure Flooded (%) |
|---|---|
| Rabun | 33.33333 |
| Gilmer | 31.25000 |
| Worth | 25.00000 |
| Union | 25.00000 |
| Glynn | 21.27660 |
| County | Health/Medical Infrastructure Flooded (%) |
|---|---|
| Pulaski | 28.57143 |
| Appling | 20.00000 |
| Jeff Davis | 20.00000 |
| Chatham | 17.02128 |
| Gordon | 11.11111 |
| County | Safety/Security Infrastructure Flooded (%) |
|---|---|
| Chattooga | 31.03448 |
| Murray | 26.53061 |
| Appling | 20.38835 |
| Toombs | 20.00000 |
| Muscogee | 17.49271 |
Given the scale at which transportation infrastructure is impacted at the state level, the top 10 are included below.
| County | Transportation Infrastructure Flooded (%) |
|---|---|
| Oglethorpe | 85.71429 |
| Pulaski | 82.22222 |
| McIntosh | 73.41772 |
| Rabun | 72.07207 |
| Baker | 70.83333 |
| Heard | 69.23077 |
| Stewart | 68.23529 |
| Bacon | 58.49057 |
| Clay | 57.69231 |
| Worth | 57.29730 |
Land Area and Lifelines Flooding Relationship
Using Re-Public community lifeline flooding data at the county level, we wanted to assess the relationships between land area flooded and lifeline flooding. 
There is little correlation between the two parameters (R^2 = 0.08651). While some of the coastal counties face very flood risk by land area, inland counties with high social vulnerability (ex. Colquitt) may deal with a large loss of critical infrastructure.
Tract Flooding & SVI
The interactive map displays social vulnerability of every tract (ranked at the state level).
The following plot shows tract-level land area flooding.
This plot shows the relative population affected (using % flooding as the proportion for population affected).
For every tract, we calculated a combined social vulnerability-flooding score by multiplying the vulnerability percentile (ranked at the state level) with the tract flooding. This graphic shows the scores from the overall vulnerability percentile.
References
- Centers for Disease Control and Prevention/ Agency for Toxic Substances and Disease Registry/ Geospatial Research, Analysis, and Services Program. CDC/ATSDR Social Vulnerability Index [2018] Database [Georgia].